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Resident Manual of Trauma to the Face, Head, and Neck

Chapter 4: Midfacial Trauma

Robert M. Kellman, MD

John M. Morehead, MD

I. Maxillary and Orbital (and Zygomatic) Fractures

Fractures of the midfacial bones are most commonly due to blunt

trauma from falls, altercations, and motor vehicle accidents. While

penetrating injuries certainly occur, they are less common, and are

typically not addressed in discussions of fractures.

A. Dental Terminology

1. Maxillae and Mandible

To clearly communicate about the anatomy and to discuss common

fractures, it is necessary to provide some terminology commonly used

to describe and classify these fractures. In addition, when discussing

fractures that involve bones that hold teeth (i.e., the maxillae and

mandible), it is important to understand the basics of occlusion.

a. Intercuspation

The maxillary and mandibular dentition interdigitate (called intercuspa-

tion) for the purpose of chewing food.

b. Crossbite

The maxillary arch is generally larger than the mandibular arch, so that

the maxillary dentition is supposed to be more lateral and anterior

(buccal and labial) than the mandibular dentition. When this does not

occur, it is referred to as a “crossbite,” which can occur unilaterally or

bilaterally. If a crossbite is not premorbid, it can be the result of a

trauma.

c. Overjet and Overbite

The “jetting” of the maxillary incisors forward of the mandibular incisors

is called “overjet,” which is a normal finding. The vertical extension of

the maxillary incisors is also normal, and is called “overbite.” Of course,

both of these can be abnormal if the distances involved are excessive or

less than optimal.

d. Angle’s Classification

The overall relation between the maxillary and mandibular dentition is

generally defined by Angle’s classification, described as the ”mesiobuc-

cal cusp of the maxillary first molar fitting into the mesiobuccal groove

of the mandibular first molar” on each side. (Keep in mind that since the

normal maxillary arch is larger, the maxillary incisors sit anterior to the